1. Field of the Invention
The present invention relates to an optical recording/regenerating apparatus, and more particularly, to a method and an apparatus that automatically controls the optimum output of a laser diode.
2. Description of the Related Art
In the information-oriented or multimedia society we live in today, recording media accommodating a large amount of data is required. These recording media include CD-Rs, CD+RWs, magnetic optical disc drives (MODDs), digital versatile disc random access memories (DVD-RAMs), DVD-RWs, DVD+RWs, and the like. These recording media use laser diodes and thus control of the optimum output of the laser diodes determines their performances. Also, different types of recording media require different types of recording pulses, and therefore effective alternative methods of recording are required.
FIG. 1 shows a block diagram of a conventional apparatus that automatically controls the output of a laser diode. Referring to FIG. 1, the apparatus includes an interface 110, a decoder 120, an address controller 130, a pulse generator 140, an ALPC block 150, an LD driver 160, and a delay unit 170.
The interface 110 communicates with an outer processor, e.g., a microprocessor of a computer to transceive information on recording/regenerating data, control data, and modes used. The decoder 120 includes an address decoder 121, a register unit 122, and a demultiplexer 123 that selects one of a variety of registers included in the register unit 122. The address controller 130 can include a variety of registers and sub-blocks to realize the functions of the address controller 130. The laser diode driver 160 is a device switching at a high speed and may include generally-used ICs or ASICs.
The pulse generator 140 generates signals that in turn generate and control recording pulses to form a domain on a recording medium corresponding to data to be recorded. Delay unit 170 is for delay, LD represents a laser diode, and PD represents a photo diode.
The ALPC block 150 detects the difference between a basic power value from the decoder 120 and a current power value from the PD and controls the laser diode driver 160 based on the detected result.
The operation of the apparatus shown in FIG. 1 is described below. The interface 110 is not described specifically because its configuration depends on each optical disk unit.
The decoder 120 selects and keeps target power values, e.g., basic power values such as read power, eraser power, and peak power. At least three or more basic power values selected, e.g., read power, eraser power, and peak power, are input into the ALPC block 150. A first D/A converter 151 converts each basic power value to an analog signal value and transmits it to a comparator 152.
Meanwhile, a signal output from the PD is transmitted to the comparator 152 via a buffer (not shown). Here, the pulse generator 140 generates a signal, and then transmits this signal to the comparator 152 via the delay unit 170 to control the operation of the comparator 152.
An up/down counter 153 counts up or down based on the results of the comparator 152. The output of the up/down counter 153 is selected by a second demultiplexer 154, converted to an analog signal via a second D/A converter 155, and transmitted to the LD driver 160.
A control signal is input into the LD driver 160 to control each power level from the ALPC block 150 and each power level from the pulse generator 140.
In the apparatus shown in FIG. 1, the up/down counter 153 is used to compare and control the basic power values and the current power values fed back to the LD driver. However, since the speed of recording and regenerating media has increased significantly, the operating speed of the up/down counter 153 limits the control speed and range. Also, as the recording speed increases, the width of recording pulses gets narrower and more complicated.